Method for simultaneously imparting an alternate series of thread forms on a workpiece



Sept. 7, 1965 G. L. WIEBER 3,204,442

METHOD FOR SIMULTANEOUSLY IMPARTING AN ALTERNATE SERIES OF THREAD FORMS ON A WORKPIECE Filed July 50, 1963 2 Sheets-Sheet l -z' fi INVENTOR. George L. Wieber Sept. 7, 1965 G. L. WIEBER METHOD FOR SIMULTANEOUSLY IMPARTING AN ALTERNATE SERIES OF THREAD FORMS ON A WORKPIEGE Filed July 50, 1965 2 Sheets-Sheet 2 Ffg 5A INVENTOR. George L. Wieber His Arr) United States Patent METHOD FOR SIMULTANEOUSLY IMPARTING AN ALTERNATE SERIES OF THREAD FORMS ON A WORKPIECE George L. Wieber, Mount Prospect, Ill., assignor to Illinois Tool Works Inc., Chicago, 111., a corporation of Delaware Filed July 30, 1963, Ser. No. 298,766 7 Claims. (Cl. 72-88) This invention relates in general to a method and apparatus for simultaneously imparting an alternate series of thread forms on a workpiece and more particularly relates to a method and apparatus for simultaneously imparting an alternate series of thread forms where one form extends radially outwardly a substantially greater amount than the next alternate form on a screw shank or the like.

The thread rolling of screw or bolt workpiece shanks is normally accomplished by thread rolling dies having parallel grooves therein, the grooves being substantially identical in configuration. In some thread rolling dies, the dies are reciprocated past each other with the path of motion of one of the dies being at a slight angle to the axis of the other die (which is usually stationary).

The instant method and apparatus relates to the use of a pair of die blocks which have reciprocatory relative motion in substantially parallel plane.

In order to provide the desired high-low thread forms alternating on the workpiece shank, it has been found necessary and desirable to provide adjacent grooves which have initially different depths in the die blocks, initially different widths, and the side walls converge at different rates along the length of the respective grooves. It has further been found necessary and desirable to provide a wide acceptance angle for the groove which provides the I radially larger thread which starts the material of the workpiece shank moving from its original grain structure with a semigentle movement rather than an abrupt change which would occur with a sharper acceptance angle.

It is a general object of this invention to provide a method and apparatus for thread rolling relatively high and relatively low threads on a screw shank in alternate arrangement.

It is a further object of this invention to provide a method and apparatus for providing screw threads of the aforenoted type in a manner which is fast, economically feasible, and provides a uniform high quality product.

A still further object of this invention is to provide a method and apparatus of the aforenoted type wherein the tooling may be made by standard techniques and which has relatively long life in actual use.

The novel features which are characteristic of the invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best be understood by the following description of a specific embodiment when read in conjunction with the accompanying drawings in which: I

FIG. 1 is a semidiagrammatic view of fixed and reciprocating die blocks and their relative relationships during the thread rolling operation;

FIG. 2 is a side elevational view indicating the product obtainable by the disclosed method and apparatus;

FIG. 3 is a semidiagrammatic side elevational view of the stationary die block shown in FIG. 1;

FIG. 4 is a semidiagrammatic side elevational view similar to FIG. 3 showing the die block which reciprocates in FIG. 1;

FIG. 5 is a semidiagrammatic showing of a plurality of outline sectional views along the grooves in the die 3,204,442 Patented Sept. 7, 1965 blocks showing the varying rates of changes in the depth and width of the grooves along the length thereof;

FIG. 5A is a sectional view along lines 5A-5A of FIG. 4, said view being considerably enlarged in scale.

FIGS. 6A through 6E are a plurality of sectional views, greatly enlarged, taken along the respective lines 6A, 6B, 6C, 6D, and 6B of FIGS. 3 and 4 indicating the various changes represented along the sectional lines and illustrate the thread forming characteristics of the die related to the flow of material axially to the workpiece as it would pass through the areas designated by lines 6A6A through 6E-6E (which are normal to the thread form) of FIGS. 3 and 4; and

FIG. 7 is a sectional view along lines 7-7 of FIG. 5A.

Means for feeding screw blanks for cooperation with a pair of relatively reciprocating die members are well known and shall not be discussed further. This invention relates to the die blocks 10 comprising a stationary die block means 12 and a reciprocating die block means 14. As shown in FIG. 1, the die block 14 is operable to move substantially parallel to die block 12 to roll threads on a workpiece 16 to provide alternate high threads 18 and relatively low threads 20 simultaneously. It will be noted that the high threads 18 extend radially outwardly a considerably greater distance than do the alternate low threads 20. The screw blank 16 has a pointed tip 24 and a head portion 22 which is cross-slotted or otherwise formed for imparting rotation to the blank. The precise form of head 22 and entering end 24 may be varied within wide limits depending upon the application desired and form no part of the instant invention.

While the die blocks 12 and 14 are of diflierent overall lengths, as is conventional the essential characteristics of each die block are the same and unless specific differences are discussed between the different die blocks, it will be assumed that the identical feature will be found on both except for considerations of left and right hand faces in opposition to each other. The die block 12 and the die block 14 are each formed with alternate grooves which are generally parallel to each other and differ from each other. The gnooves traverse the die block at a predetermined angle as determined by the lead and diameter of the finished screw desired. As shown in FIGS. 3 and 4 the grooves 26 and 30 in full line are shallower grooves relative to grooves 28 and 32 shown in dotted line. The shallower grooves impart the thread form 20 on the screw blank whereas the deeper grooves 28 and 32 impart a thread form 18 on the screw blank.

As can be perceived intuitively from FIGS. 5 and 5A, each of the grooves 26, 30 and 28, 32 progressively vary in width and depth along the length thereof and at different rates relative to each other. As shown in FIG. 5, outline sectional views taken as indicated along FIGS. 3 and 4, indicate the progressive change along the length of the grooves. FIGS. 6A through 6E correspond to the outline sectional views and show the gathering of the material from the screw blank as the thread is being formed.

The stationary die block 12 has an entering end portion 34 and a trailing end portion 36 wherein the operating face of the die block is recessed slightly for respectively facilitating entrance of the screw blank and removal of same from between the die blocks as is conventional. Each of the die blocks 12 and 14 have an ironing portion 38 where the grooves are of constant width and depth for a predetermined portion of the groove length for purexcept for overall absolute length.) The groove 32 for forming the thread 18 has opposed side walls 42 and 44 and a bottom wall 46 which changes in character at 48 as shall be described. As can be seen in FIG. 5A, the side walls 42 and 44 progressively converge toward each other and the bottom wall 46 progressively comes closer to the operating face 40, i.e., the groove becomes progressively shallower for a major portion of its length. This is perhaps best illustrated in FIG. 7. The groove 32 may be formed by first passing a cutter having an outline shape as shown at 6B in FIG. 5 across the die face parallel to surface 40 and then passing a cutter having an outline shape such as shown in FIG. 6A across the face 40 while progressively relatively moving the cutter and die block on an angle to each other so that the groove becomes shallower. After the second cutter has run out with the first cutter (for example a 30 cutter) the second cutter (for example a 60 cutter) having an outlined form as shown at 6A is superimposed upon the first groove, said second cutter being moved at an inclination ,angle relative to the die block so that the depth of the groove blends into the form 6E. The narrower angle cutter forms the bottom surface 48 of the groove and the intersection where the two cutters remove the stock and blend together on the different angles is shown at 50 in FIG. 7, the slope of the side walls 42 and 52 are different, caused by the different angularities of the two different cutters. The groove 30 is formed by a single cutter (for example a 60 cutter) to provide side walls 54 and 56 which are converging toward each other and a bottom wall 58 which is moving toward surface 40 at a constant rate along the length thereof except for ironing portion 38.

As shown in FIGS. 6A through 6E, a blank interposed between the tWo die blocks 12 and 14 will form the threads 18 and 20. FIG. 6A is a sectional view showing the gathering of the material approximately at the start of the thread forming operation. The wide acceptance angle of groove 32 at the start of the groove is efficacious to gather the material from the screw blank 16. FIG. 6B is a projection at approximately 30% of the thread transformation, it being noted that thread portion 20b is quite well filled out whereas thread portion 18b is not. The projection in FIG. 6C shows the thread 200 is almost completely filled out whereas 180 is not formed, the projection being taken at approximately 60% of the thread transformation. The projection shown in FIG. 6D shows that the thread 20 is not fully formed whereas thread portion 18d is only about 90% formed and FIG. 6E shows the complete thread formation of both threads 18 and 20 at the finished portion of the die. FIGS. 6A through 6B are actual projections respectively of onehalf, three, five and seven turns of a screw blank on a thirty times size scale. However, it will be realized that in rolling screws, the percentage of thread forming transformation per turn of the blank will vary depending upon size of blanks, etc.

The ironing section 38 on the die block allows the screw blank to regain a circular shape from an oval shape and trues up the threads. The threads that are formed by this method are found to be quite strong and well formed.

It will be noted as shown in FIG. 6A that the groove 32 has a wide mouth which provides a wide acceptance angle which starts the material moving on the screw blank from its original grain structure toward forming the very high thread with a semigentle movement rather than an .abrupt change that would occur with a much narrower mouth. It will be further noted that the grooves 30 and 32 are of different depths along the length thereof, are of different widths along the length thereof and that the grooves converge at different rates. Also it will be noted that the low thread 20 is fully formed prior to the formation of the higher thread 18.

Although a specific embodiment of the method and apparatus for simultaneously forming high and low threads on screw blanks have been shown and described, it is with full awareness that many modifications thereof are possible. The invention therefore, is not to be restricted except insofar as is necessitated by the prior art and by the spirit of the appended claims.

I claim:

1. The method of forming high and low threads on a cylindrical screw blank located between opposed dies comprising the steps of relatively moving the dies and the blank, by said moving of dies and blank displacing material for the high threads at a first rate, and displacing material for the low threads at a second rate which is less than said first rate, and decreasing the rates of displacing material for both high and low threads as said moving of die and blank proceeds.

2. The method set forth in claim 1 including the step of ironing the respective threads after forming same to true up the threads and the blank.

3. The method set forth in claim 1 wherein relatively moving the dies and the blanks imparts a rolling movement to the blank in a plane parallel to the long axis of the blank.

4. The method set forth in claim 1 wherein the rate of displacing the material for forming the high thread is varied during the formation of the thread.

5. The method according to claim 1 wherein the rates at which the material is displaced and the threads formed are determined by the diminishing depths, widths and degrees of wall convergence of the thread-forming grooves in the dies.

6. The method of forming high and low threads on a cylindrical screw blank located between opposed dies comprising the steps of relatively moving the dies and the blank, by said movement displacing material for the high threads at a first rate, displacing material for the low threads at a second rate which is less than said first rate, and forming completely the low threads before forming completely the high threads.

7. The method according to claim 6 wherein the rates at which the material is displaced and the threads formed are determined by the diminishing depths, widths and degrees of wall convergence of the thread-forming grooves in the dies.

References Cited by the Examiner UNITED STATES PATENTS 370,354 9/ 87 Rogers 9 425,035 4/90 Jones 809 2,183,688 12/39 Olson 809 2,562,516 7/51 Williams 8061 2,679,774 6/54 MacDonald 8061 2,760,3' 88 8/ 5 6 Seibert 809 3,019,677 2/62 Cermatori 809 3,069,941 12/62 Baubles 806 CHARLES W. LANHAM, Primary Examiner. MICHAEL V. BRINDISI, Examiner. 

1. THE METHOD OF FORMING HIGH AND LOW THREADS ON A CYLINDRICAL SCREW BLANK LOCATED BETWEEN OPPOSED DIES COMPRISING THE STEPS OF RELATIVELY MOVING THE DIES AND THE BLANK, BY SAID MOVING OF DIES AND BLANK DISPLACING MATERIAL FOR THE HIGH THREADS AT A FIRST RATE, AND DISPLACING MATERIAL FOR THE LOW THREADS AT A SECOND RATE WHICH IS LESS THAN SAID FIRST RATE, AND DECREASING THE RATES OF DISPLACING MATERIAL FOR BOTH HIGH AND LOW THREADS AS SAID MOVING OF DIE AND BLANK PROCEEDS. 